There is a technique of shortening a track width of a magnetic disk and of increasing a track density in order to increase the capacity of a hard disk drive (hereinafter, referred to as HDD) and to improve a recording density.
Further, there is disclosed a technique of narrowing the track width to an extent that the adjacent tracks are partially overlapped and overwritten in order to improve the track density of the magnet disk. This technique is called a shingled magnetic recording technique. In a case where the shingled magnetic recording technique is used, the data of the adjacent tracks partially overlapped overwritten is erased at the time of writing. Therefore, there is a need to perform writing in unit of a track group (hereinafter, referred to as band) by collecting a plurality of tracks.